Contribution of vegetation to methane emission produced in the soil of an upland forest: a 13CH4-labelling approach

The role of vegetation on net methane fluxes from upland forest ecosystem has only recently been underlined and is still not fully understand and quantify. Indeed, influences of forest plants on the methane budget could be antagonist, being a net methane producer or emitter in some cases or enhancing the methane consumption in others. But the vegetation in upland forests decreases the net methane uptake by 0 to 63%, and in a few cases, increases the methane uptake up to twice. One of the mains source of methane emission related to the vegetation is the transport of methane from deep anoxic soil layers where the methane is produced to the atmosphere through plant stems.

In order to quantify if vegetation is a preferential way of methane emission in our field site, a ¹³CH₄ labelling had been undertaken in soil (at 40 cm depth) and ¹³CH₄ had been traced in upper soil layers (0, 5, 10, 25 cm depth), on the soil surface with soil chambers with or without herbaceous vegetation and in tree stem chambers for two days after the pulse labelling.

¹³CH₄ was recovered in all compartments even though the forest ecosystem was mainly a methane sink during this period when methane uptake dominated.

In our study, the vegetation (tree stems and herbaceous vegetation) have a limited contribution on the recovery of ¹³CH₄ at the forest scale, which is dominated by soil emissions.